Understanding the partial pressure of oil and gas
Thread Content
I have always been unclear about vapor pressure. After reading the first two posts on vapor pressure, I developed the following idea: 1. When the total pressure at the top of the tower remains constant, increasing the vapor pressure of one component is equivalent to decreasing the vapor pressure of another component； 2. As the partial pressure decreases, the boiling point drops as well; with the top temperature remaining unchanged, the dry point of the oil naturally increases ； Is this understanding correct? Seek advice!
This post was last edited by ylb913 on 2018-9-9 at 17:58. The first sentence is correct; the second sentence seems to refer to an increase in the initial boiling point rather than a general increase in the boiling point.
Thank you for the answer! I didn’t explain myself clearly; what I meant was the product at the top of the tower. If we use the product from the bottom of the tower, then the initial boiling point will increase.
This post was last edited by longziyun on 2018-9-10 23:22. The original poster is incorrect; in the top of a distillation column, there is no such concept as partial pressure for highly concentrated single components or similar mixed components. This term is only applicable in separation columns, such as those used in catalytic cracking or stabilization processes. “1. When the total pressure at the top of the tower remains constant, increasing the partial pressure of one component is equivalent to decreasing the partial pressure of another component ； 2. As the partial pressure decreases, the boiling point drops as well; with the top temperature remaining unchanged, the dry point of the oil naturally increases ； ” 1 is correct. 2 is a bit inaccurate; “the partial pressure decreases.” It’s not clear whether it is the partial pressure of the light components or that of the heavy components that decreases, as the resulting effects differ. It should be a decrease in total pressure, ...... Take the distillation tower as an example: normally, the top of the tower produces gasoline and liquefied gas components that are heavier than light diesel. When the total pressure decreases while the temperature at the top remains unchanged, as you said, the dry point of the oil products increases, which causes the light diesel fraction to end up in the gasoline fraction, resulting in a higher dry point for gasoline. However, this does not comply with national standards and constitutes illegal operation. :lol